Method

1. Rinse the rice well in a sieve and then put into a small saucepan of 250ml of water and a pinch of salt. Bring to the boil, then reduce the heat and cover with a lid. Simmer for 25 minutes without lifting off the lid, then turn off the heat and leave to sit for another 10 minutes for perfectly cooked rice (or simply cook according to packet instructions). This rice can sit for 30 minutes with the lid on.
2. Preheat the oven to 160°C/ 325°F/ Gas Mark 3.
3. Using a small knife, cut the onion in half and peel off the skin, then on a chopping board, cut into slices, keeping the root intact. Then make 2 horizontal cuts, one above the other, and finally chop across the width of the onion.
4. Cut the peppers in half and remove the seeds and core with a teaspoon, then finely chop into dice.
5. Peel the garlic and then use a garlic crusher or grate the garlic on the fine side of a box grater. 
6. Place the tomatoes, peppers, onion, garlic, paprika, salt, chilli, if using and cumin a heavy casserole dish. Cut the chicken into bite-sized pieces and add to the casserole dish and spoon the ingredients on top to ensure they cover the chicken.
7. Remember to wash your hands with warm soapy water after handling raw chicken.
8. Cover with a lid and place in the oven for 1 hour until the chicken can be shredded easily with two forks. 
9. Fold in the black beans and rice and continue to cook until heated through. Grate the cheese then divide the spicy chicken and rice bowls and garnish with the cheese and some sour cream.